Conveyor systems are commonly used to move product or materials from one location to another. Conveyor belt systems accomplish this by typically using a moving belt or a conveyor type belt to power live roller conveyors. A conventional conveyor belt system may have two or more pulleys and the moving, continuous belt that rotates around the pulleys. The belt is usually driven by some type of powered pulley or other mechanism that urges the belt around the pulleys. The system may be a simple one belt system, or may be a more complex system having multiple conveyor belt sections, where each section is configured to have a particular belt and move product or materials from one section to another.
Conveyor belts used in such systems have a characteristic service life, which may depend upon many factors. Those skilled in the art will appreciate that these factors may include, but are not limited to, the type and quality of the belt and splice joining the ends of the belt, the weight and shape of the belt, the bends in the conveyor system, pulley lagging, tension, etc.
For proper system operation and to best take advantage of the belt's possible service life, it is important to maintain an appropriate level of belt tension on a belt within a conveyor. Conventional conveyor systems are known to use a take-up pulley or bearing, which may be selectively moved relative to other pulleys in the system in order to maintain a relatively constant and desired level of belt tension.
Belt manufacturers typically recommend a range for anticipated belt stretching as part of an initial tensioning guideline, but accurately measuring belt tension as it is initially installed or at any time during its life can be problematic. A belt usually stretches over time, especially during an initial break-in use period. Belt stretching or expansion necessarily reduces belt tension, which can lead to various undesirable problems with a conveyor system. For example, one skilled in the art will appreciate that improper belt tension may result in problems such as belt reversion (i.e., softening and deterioration of the belt material), imbalance of belt wear, slippage under load, higher energy consumption for the system, heat losses, belt failure, drive failures, premature bearing wear, drive pulley shaft deflection, seized conveyors, and the like. Things that may affect belt tension and belt stretch include the type of belt, the material and uniformity of the belt, the width and length of the belt, product weight on the belt to be conveyed, drive roller surface, belt arc on the drive pulley/roller contact, and the like.
Conventional methods for tensioning belts are known to be imprecise, overly cumbersome, or may require an undesired level of support resources. One conventional rule of thumb for determining a proper belt tension is to stop the conveyor and depress the belt near a crowned pulley to see if there is any visible play between the pulley and the belt. In other words, if the belt tension is not high enough to force the belt to conform to the crown on a crowned pulley, poor tracking will likely result and an increase in belt tension is warranted. However, this method is imprecise at best and difficult to repeat with respect to different operators or the same operator attempting to set the same tension at different times.
Another classic belt tensioning procedure involves making two marks on the top side of the belt under zero tension, and then increasing the tension to the belt until it stretches to the manufacturer's recommended percentage of stretch. As such, the belt may be initially over-tensioned to account for a typical belt stretch range (e.g., 0.3% to 2.0% belt stretch). However, this method is often vague and imprecise in that it may not take into account a variety of different conveyor configurations and applications.
Another way to measure belt tension is to precisely model the conveyor and account for all factors that impact tension. However, this is known to be computationally difficult, multi-faceted in the different types of factors involved, and cumbersome for service personnel. For example, belt manufacturers may attempt to estimate belt tension when supplied with additional information relative to a belt installation, such as loading and pulley configuration information. Calculation tools may attempt to model some of the variables that affect the tracking and tensioning of a conveyor belt, but this is computationally intensive and will change very quickly over time and with any change in the system requiring an undesirably high-level of engineering support and cost to determine belt tension.
As a result, conveyor system operators may over tension the belts because of a lack of an easy way to accurately measure belt tension. Thus, there remains a need for an apparatus and system that allows for an easier and quicker way to measure belt tension within a conveyor system.